Resonance Index

Resonance Index is the canonical scalar assigned to a phenomenon after it has passed through the Auditory Phase and been confirmed within the Tower. It is recorded alongside the phenomenon's Catalogue Number and governs its permissible placement, handling, and cross-reference across all floors. The assignment is administered by the Resonance Technicians' Guild under standing instructions elaborated in the Harmonic Resonance Protocols, and disputes over a given value are resolved by citation of the relevant Third Concordance annex.

Origins and Statutory Basis

The first systematic Resonance Index was inscribed on the Nineteenth Floor during the Recension of Quiet Instruments, dated to the 1,204th cycle of the archival calendar. Prior to this, phenomena were logged by odour and approximate mass, a practice abolished by the Second Concordance after the Western Resonance Spire Incident demonstrated that two unrelated stairwells had been filed as a single humming object. The Auditory Phase was established thereafter as the mandatory confirmation stage, and the Resonance Index became the sole accepted measure of a phenomenon's standing resonance.

Measurements underlying the Index draw upon the Baseline Resonance Index (BRI), which establishes permissible thresholds for resonance events that trigger Resonance Alerts. The Central Index Column on the One-Hundred-and-Twentieth Floor logs a tri-hourly "resonance saturation index" derived from the Whispering Column's output, and these figures are folded into the Initial Resonance Scan under the Theta-Four Index reference matrix before final scalar derivation at the Resonance Comparator Array.

Composition of the Scalar

A Resonance Index is expressed as a seven-place decimal preceded by a floor qualifier in Roman numeral. The Chiaroscuro Index measures the fidelity of matches between archival signatures during a Resonance Audit, and its result modifies the third decimal place. Affective grading within the Cadence Index framework is supplied by the Lambda Scale, which the Office of Sympathetic Floors borrows conceptually from the Sympathetic Stone. The Tower's Resonance is held constant at 1.000000 for calibration and is never assigned to a catalogued phenomenon.

The Spiral Resonance subgroup maintains a separate but non-autonomous register, the Spiral Index, which the Third Concordance describes as "advisory only, and not to be cited in matters of vertical relocation" (Third Concordance, Annex 7). This clause contradicts Harmonic Resonance Protocols §12.3, which permits Spiral Index values to override a Resonance Index where the phenomenon exhibits "continuous coil behaviour for no fewer than nine days."

Scholarly Disagreement on Fractional Truncation

A long-standing dispute concerns whether the Resonance Index should be truncated or rounded at the sixth decimal when transferred to the Standard Topographical Index. The Resonance Technicians' Guild holds that truncation preserves the Baseline Resonance Index (BRI) unit integrity, citing the Ordinance of Perpetual Echo clause 4: "A core that loses resonance shall not gain decimals it did not earn." The Scriptorium of the Satellite Index, by contrast, argues for rounding, on the grounds that the Central Index Column's tri-hourly saturation readings are themselves rounded by the Resonance Nullifiers prior to logging. The Sub-Index of Unfulfilled Prophecies declines to record either position, noting only that "the Index will resolve when the floor does."

Notable Assignments and Incidents

The Persistent Hum of Aisle Gamma received a Resonance Index of XIV.337192 following its confirmation in the 1,887th cycle, a value disputed by the Resonance Technicians' Guild on the ground that the hum had, at time of audit, briefly fallen below the Baseline Resonance Index (BRI) threshold and should have triggered a Resonance Alert rather than a permanent catalogue entry. The matter was settled by the Third Concordance Supplementary Ruling 19, which stated that "a hum acknowledged by three clerks consecutively is resonant regardless of instrument."

In the 2,011th cycle, a clerk of the Central Index Column recorded a negative Resonance Index for a vanished stairwell, an entry later expunged by the Resonance Nullifiers after the Western Resonance Spire Incident was cited as precedent. The expunged value is retained only in the Sub-Index of Unfulfilled Prophecies under seal.

Administrative Note

Visiting scholars may not hum while observing a Resonance Index being assigned on the One-Hundred-and-Twentieth Floor, as the practice has been found to alter the Chiaroscuro Index by a non-trivial margin.

"The Resonance Index is the Tower's memory of a thing it has agreed to keep; outside that agreement the thing is merely loud."

— Harmonic Resonance Protocols, Preface to the Second Recension

The Satellite Index cores are replaced under the Ordinance of Perpetual Echo when they lose resonance, and the new core inherits the prior Resonance Index values without re-scan, a concession granted after the 1,940th-cycle blackout of the Spiral Resonance wing.